The prior art discloses various methods for the preparation of alkaryl sulfonates, many of which involve the use of high percentages of water which must be eliminated in order to obtain a relatively dry product. As a result, they require high energy inputs and prolonged processing times to produce the desired end product, factors which contribute significantly to the cost of producing sulfonates by such methods.
U.S. Pat. No. 2,928,867, issued Mar. 15, 1960, to Kirk, et al, for example, discloses a method for preparation of stable alkaryl sulfonates. The method involves the use of alkaryl hydrocarbons such as dodecylbenzene to which is added sulfur trioxide. After cooling, a substantial quantity of water is then added, after which the solution is mixed and then neutralized with a 14% sodium hydroxide solution which, of course, increases the amount of water already in the reaction mixture.
U.S. Pat. No. 4,144,266, issued Mar. 13, 1979, to Plummer, et al, discloses a method for the sulfonation of crude oil to produce petroleum sulfonates by treating a crude oil with sulfur trioxide, removing unreacted hydrocarbons by the addition of water, and then neutralizing the formed sulfonic acid with a base.
U.S. Pat. No. 2,847,459, issued Aug. 12, 1959, to Mitchell, is directed to the preparation of aromatic sulfonate salts wherein a higher alkaryl substituted aromatic compound is first reacted with anhydrous sulfur trioxide. The resulting acid mix is then neutralized by pouring it into a vessel containing water and an alkali metal hydroxide. The slurry, containing the neutralized product, is "aged" at a temperature of approximately 65.degree. C. to about 100.degree. C. to provide a water-soluble alkayl aryl sulfonate having a substantially stable pH. Water comprises from 20% to 80% by weight of the mixture being aged.
U.S. Pat. No. 3,358,017, issued Dec. 12, 1967, to Seifert, relates to a process for producing substantially odorless alkaryl sulfonates by, in part, neutralizing an alkylaryl sulfonic acid with aqueous sodium hydroxide.
British Pat. No. 958,995, discloses a process for the preparation of alkyl-aryl sulfonates which involves first, sulfonating an alkyl-aryl compound, then neutralizing said compound with an aqueous solution of alkali metal hydroxide and cooling said neutralization mixture.